FIG. 1 is a schematic diagram illustrating a configuration of contactless power transmission apparatus 106 according to the related art. In FIG. 1, a power feeding apparatus (primary side) F connected to a power panel of power supply 109 on a ground side is disposed so as to face a power receiving apparatus (secondary side) G with an air gap interposed in between and without any physical contact during power supply. This air gap is a void space. Power receiving apparatus G is mounted on an electric propulsion vehicle. In such a configuration, when an alternating current (AC) is given to primary coil 107 (power feeding coil) provided for power feeding apparatus F and a magnetic field is generated, an induced electromotive force is generated in secondary coil 108 (power receiving coil) provided for power receiving apparatus G. Power is thereby transmitted contactlessly from primary coil 107 to secondary coil 108.
Power receiving apparatus G is connected to, for example, vehicle-mounted battery 110, and vehicle-mounted battery 110 is charged with the power transmitted as described above. Vehicle-mounted motor 111 is driven by the power stored in battery 110. Note that necessary information is exchanged between power feeding apparatus F and power receiving apparatus G during contactless power supply processing via, for example, wireless communication apparatus 112.
FIGS. 2A and 2B are schematic diagrams illustrating an inner structure of power feeding apparatus F and power receiving apparatus G. Particularly, FIG. 2A is a schematic diagram illustrating an inner structure of power feeding apparatus F seen from above and power receiving apparatus G seen from below. FIG. 2B is a schematic diagram illustrating an inner structure of power feeding apparatus F and power receiving apparatus G seen laterally.
In FIGS. 2A and 2B, power feeding apparatus F includes primary coil 107, primary magnetic core 113, back plate 115 and cover 116 or the like. Briefly, power receiving apparatus G has a structure symmetric with respect to power feeding apparatus F and includes secondary coil 108, secondary magnetic core 114, back plate 115, and cover 116, for example. Surfaces of primary coil 107 and primary magnetic core 113 and surfaces of secondary coil 108 and secondary magnetic core 114 are respectively covered fixedly with mold resin 117 into which foamed material 118 is mixed.
Here, a relationship between primary coil 107 of power feeding apparatus F and secondary coil 108 of power receiving apparatus G in the related art will be described using a schematic diagram in FIG. 3. As illustrated in FIG. 3, primary coil 107 and secondary coil 108 are formed by spirally winding litz wires 121 and 122 which are a bundle of a plurality of elemental wires. When a vehicle is parked in a predetermined parking space, primary coil 107 of power feeding apparatus F on the ground side is disposed so as to face secondary coil 108 of power receiving apparatus G mounted on the vehicle. With primary coil 107 and secondary coil 108 facing each other, and a magnetic field generated from primary coil 107 interlinking with secondary coil 108 over a wide range, power is transmitted contactlessly.